**3. Methods of TCA analysis in cork stoppers**

Cork stoppers may eventually contain at least traces of haloanisoles, in particular TCA. However, wines bottled with cork stoppers only rarely have noticeable musty/moldy defects. The reason lies in the particularities of the extraction of TCA by wine from the cork material. Wine is an aqueous solution of alcohol with a moderate extraction power in relation to TCA, while the cork material retains this compound rather strongly [46]. In addition, TCA can be efficiently extracted only from the part of the cork that is in direct contact with wine. No noticeable migration of TCA from the middle or outer part of cork stoppers into bottled wine is usually observed [40]. Consequently, the amount of TCA extracted by wine is far from the entire TCA content inside corks. According to different authors, the part of TCA that can be released into wine from a cork stopper typically varies between 0.05% and 8% [3, 33, 47, 48]. Considering these peculiarities, two concepts of TCA contamination of cork stoppers were introduced:


In general, *releasable TCA* depends on *total TCA* content and its localization in the cork stopper. Determination of *releasable TCA* content has an extensive practical application. Namely, it corresponds to the amount of TCA, which can potentially migrate and contaminate bottled wine. Therefore, it became a routine technique to control *releasable TCA* content in cork stoppers at different stages of their production. On the contrary, *total TCA* analysis most often serves as an important tool for scientific purposes. It allows to study the nature and origin of cork contamination, the distribution of TCA inside corks [49], the dynamics of TCA absorption by cork material from wine [46] or from the air [37], etc. For example, it was found that TCA content in the lenticel and non-lenticel cork fractions did not differ considerably, as well as TCA concentration in the light and dark parts of the growth rings [49]. Analytical approaches to determining *releasable TCA* and *total TCA contents* are comprehensively discussed in our review [50], including the particularities of the described methods: sample preparation and treatment techniques, TCA recovery, detection of other analytes (haloanisoles and halophenols), etc. In the current book chapter, this information is summarized in the following subsections.
